1. Field of the Invention
This invention relates to a method for removing catalyst-poisoning impurities or contaminants such as arsenic and selenium, from hydrocarbonaceous fluids, particularly shale oil and fractions thereof. More particularly, the invention relates to a method of removal of such impurities by contacting the fluids with high-sodium alumina. The high-sodium alumina may be used as a guard bed material in a step preceding most refining operations, such as desulfurization, denitrogenation, catalytic hydrogenation, etc.
2. Description of the Prior Art
Due to scarcity of other hydrocarbon fuels and energy resources in general, shale oil and other hydrocarbonaceous fluids such as those derived from coal, bituminous sands, etc., are expected to play an increasing role in the production of commercial hydrocarbon fuels in the near future. Substantial effort is being devoted to the development of cost-efficient refining techniques for the processing of these hydrocarbonaceous fluids. Frequently, these fluids contain contaminants that poison and deactivate expensive and sensitive upgrading catalysts used in hydrogenation and other refining steps to which these hydrocarbonaceous fluids must be subjected before they can be satisfactorily used as sources of energy. In addition, the removal of contaminants such as arsenic may be necessary for environmental protection if the hydrocarbonaceous fluids are employed as fuels, as these contaminants form poisonous compounds.
The prior art has included several methods of removing arsenic from hydrocarbon-charged stocks, such as that described in U.S. Pat. No. 2,778,779 to Donaldson issued on June 14, 1952. Such methods have included the use of ferrous metal oxides to remove arsenic from streams of naturally occurring crude oil.
Other processes have been developed for the removal of arsenic in the parts per billion range from naphthas in order to protect sensitive reforming catalysts. Unfortunately, such processes cannot be applied to shale and other hydrocarbonaceous fluids which often have arsenic concentrations as high as 60 ppm.
Also known, are washing processes employing aqueous caustic solutions to precipitate arsenic salts from the hydrocarbonaceous fluid and extract them into the aqueous phase. See, e.g. U.S. Pat. No. 2,779,715 to Murray issued on Jan. 29, 1957 and D. J. Curtin et al. "Arsenic and Nitrogen Removal during Shale Oil Upgrading," A.C.S. Div. Fuel Chem., No. 23(4), 9/10-15/78. These processes, however, are relatively expensive, cause a substantial amount of fluid to be lost to the aqueous phase, contaminate the hydrocarbon fluid with aqueous solution and present a problem with regard to the disposal of waste caustic solution.
Many patents have issued which are directed to use of a metallic oxide and/or sulfide catalyst such as iron, nickel, cobalt or molybdenum oxide or sulfide or composites thereof on an alumina carrier to remove arsenic and other similar contaminants from shale oil. See, e.g. U.S. Pat. No. 4,003,829 to Burget et al. issued on Jan. 18, 1977, U.S. Pat. No. 4,141,820 to Sullivan issued on Feb. 27, 1979 and U.S. Pat. Nos. 3,954,603 to Curtin, 3,804,750 to Myers and 4,046,674 to Young. While these processes are effective, they employ relatively sophisticated and relatively expensive catalysts which considerably contribute to the processing costs of shale oil.